1. Technical Field
The present application relates generally to a radio communication system and, more particularly, to a method for accessing a base station by mobile stations, which provides a reduction in access time and prevents collisions between access requests made from a plurality of mobile stations on the same access channel.
2. Description of the Related Art
In general, as shown in FIG. 1, a plurality of mobile stations (MSs) MS#1-MS#n are wirelessly connected to a single base station (BS) 100 in a radio communication system. Although mobile stations can generally be applied to various fields, FIG. 1 illustrates mobile stations MS#1-MS#n being mounted on a vehicle.
Conventionally, in order to accomplish communication between the base station 100 and one of the mobile stations MS#1-MS#n, an access operation (i.e., an access request by the mobile station and an access approval by the base station) through a specified access channel must first be performed. The mobile station transmits an access request signal to the base station through one of a plurality of access channels to communicate with the base station. If the access requested channel is not currently occupied, the mobile station can communicate with the base station via the access channel. If the access requested channel is already occupied, however, or if two different mobile stations MS#1 and MS#2 simultaneously make access requests through the same access channel RCH#1 (as illustrated in FIG. 2), a collision will occur between the access requests, which prevents either mobile station from accessing the base station. In this situation, the mobile stations will attempt to access the base station after some time.
Referring to FIG. 3, another conventional method for accessing a base station involves allocating time slots TS#1-TS#n to the mobile stations MS#1-MS#n, respectively, so as to prevent potential collisions among the mobile stations during access request operations. One disadvantage to this method, however, is that a longer access time is required for accessing the base station 100 since the mobile stations MS#1-MS#n can only make access requests during their allocated time slots. For instance, even if mobile station MS#2 does not make an access request, mobile station MS#3 cannot use the time slot TS#2 allocated to MS#2, and can only make an access request during the allocated time slot TS#3 after the passage of time slot TS#2.